Their factory was staffed by workers from Ukraine and Bulgaria who were forced to work 12-plus hours a day in "very unhealthy" conditions, said law enforcement officers.

The criminals had even created their own cigarette brand, Spanish police said after the takedown.

According to Europol, the EU's primary law enforcement agency, eight searches were launched across Granada and Malaga in collaboration with local police.

During the searches, 10 tonnes of tobacco leaves, four tonnes of fine-cut tobacco and 4.5 million cigarettes, plus machinery, filters, paper and glue, were seized.

Seven Ukrainian workers were arrested in the factory. Three individuals were arrested in Granada and eight more were arrested in Malaga.

The alleged gang members, Europol said, stand accused of involvement in the illicit tobacco trade, participating in an organised criminal group, money laundering and violating the rights of workers.

"Illegal manufacturing of cigarettes and tobacco smuggling generate a large amount of illegal money," said Simon Riondet, head of Europol's Financial Intelligence Group.

"Criminals need to launder this illicit cash. Thus investigative efforts must target the financial assets of the criminal organisations, conveying the message that those who benefit from criminal money cannot enjoy it in the European Union."

The police effort was spearheaded by the Spanish Guardia Civil but launched in collaboration with Europol and the State Border Guard Service of Ukraine.

Also involved were the European Union Border Assistance Mission to Moldova, Bulgarian Police of the Ministry of Interior, the Romanian Guard Police and the Greek Police.

Europol said it had "supported the investigation since the beginning by providing continued analytical and operational support".

In a release on Wednesday (6 December) it said that its agents were on the scene to help with "real-time cross-checks and analysing of data".

Police arrested 18 suspected members of the suspected criminal gangEuropol